================================================================== BUG: KASAN: use-after-free in handle_userfault+0x21c1/0x24c0 fs/userfaultfd.c:371 Read of size 8 at addr ffff8801d2c59588 by task syz-executor1/6767 CPU: 1 PID: 6767 Comm: syz-executor1 Not tainted 4.15.0-rc1+ #199 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 print_address_description+0x73/0x250 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report+0x25b/0x340 mm/kasan/report.c:409 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430 handle_userfault+0x21c1/0x24c0 fs/userfaultfd.c:371 do_anonymous_page mm/memory.c:3161 [inline] handle_pte_fault mm/memory.c:3934 [inline] __handle_mm_fault+0x2cc1/0x3ad0 mm/memory.c:4060 handle_mm_fault+0x334/0x8d0 mm/memory.c:4097 __do_page_fault+0x5c9/0xc90 arch/x86/mm/fault.c:1429 do_page_fault+0xee/0x720 arch/x86/mm/fault.c:1504 page_fault+0x22/0x30 arch/x86/entry/entry_64.S:1094 RIP: 0010:__clear_user+0x42/0x70 arch/x86/lib/usercopy_64.c:23 RSP: 0000:ffff8801c7197b88 EFLAGS: 00010202 RAX: 0000000000000000 RBX: 0000000000000008 RCX: 0000000000000008 RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000020012e40 RBP: ffff8801c7197b98 R08: ffff8801d78da118 R09: 1ffff10038e32f45 R10: ffff8801d503c400 R11: 0000000000000000 R12: 0000000020012e40 R13: ffff8801d503c400 R14: 0000000020012c40 R15: 00007ffffffff000 copy_xregs_to_user arch/x86/include/asm/fpu/internal.h:372 [inline] copy_fpregs_to_sigframe arch/x86/kernel/fpu/signal.c:126 [inline] copy_fpstate_to_sigframe+0x196/0x470 arch/x86/kernel/fpu/signal.c:177 get_sigframe arch/x86/kernel/signal.c:284 [inline] __setup_rt_frame arch/x86/kernel/signal.c:465 [inline] setup_rt_frame arch/x86/kernel/signal.c:699 [inline] handle_signal arch/x86/kernel/signal.c:743 [inline] do_signal+0x9f6/0x1ee0 arch/x86/kernel/signal.c:811 exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158 prepare_exit_to_usermode+0x2e1/0x340 arch/x86/entry/common.c:195 retint_user+0x8/0x18 RIP: 0033: (null) RSP: 002b:0000000020013008 EFLAGS: 00010217 RAX: 0000000000000000 RBX: 0000000000758020 RCX: 00000000004529d9 RDX: 0000000020059ffc RSI: 0000000020013000 RDI: 0000000000000400 RBP: 0000000000000047 R08: 0000000020058ffd R09: 0000000000000000 R10: 000000002005d000 R11: 0000000000000212 R12: 00000000006ed748 R13: 00000000ffffffff R14: 00007f56ce9c76d4 R15: 0000000000000000 Allocated by task 6747: save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3547 dup_userfaultfd+0x21c/0x890 fs/userfaultfd.c:659 dup_mmap kernel/fork.c:662 [inline] dup_mm kernel/fork.c:1197 [inline] copy_mm+0xa38/0x1310 kernel/fork.c:1251 copy_process.part.36+0x1ec4/0x4ae0 kernel/fork.c:1753 copy_process kernel/fork.c:1566 [inline] _do_fork+0x1ef/0xff0 kernel/fork.c:2045 SYSC_clone kernel/fork.c:2155 [inline] SyS_clone+0x37/0x50 kernel/fork.c:2149 do_syscall_64+0x26c/0x920 arch/x86/entry/common.c:285 return_from_SYSCALL_64+0x0/0x75 Freed by task 6747: save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3491 [inline] kmem_cache_free+0x77/0x280 mm/slab.c:3749 userfaultfd_ctx_put+0x50c/0x740 fs/userfaultfd.c:165 userfaultfd_event_wait_completion+0x86d/0xae0 fs/userfaultfd.c:605 dup_fctx fs/userfaultfd.c:693 [inline] dup_userfaultfd_complete+0x2de/0x480 fs/userfaultfd.c:701 dup_mmap kernel/fork.c:730 [inline] dup_mm kernel/fork.c:1197 [inline] copy_mm+0xe9b/0x1310 kernel/fork.c:1251 copy_process.part.36+0x1ec4/0x4ae0 kernel/fork.c:1753 copy_process kernel/fork.c:1566 [inline] _do_fork+0x1ef/0xff0 kernel/fork.c:2045 SYSC_clone kernel/fork.c:2155 [inline] SyS_clone+0x37/0x50 kernel/fork.c:2149 do_syscall_64+0x26c/0x920 arch/x86/entry/common.c:285 return_from_SYSCALL_64+0x0/0x75 The buggy address belongs to the object at ffff8801d2c59400 which belongs to the cache userfaultfd_ctx_cache of size 400 The buggy address is located 392 bytes inside of 400-byte region [ffff8801d2c59400, ffff8801d2c59590) The buggy address belongs to the page: page:ffffea00074b1640 count:1 mapcount:0 mapping:ffff8801d2c59000 index:0xffff8801d27fa940 flags: 0x2fffc0000000100(slab) raw: 02fffc0000000100 ffff8801d2c59000 ffff8801d27fa940 0000000100000008 raw: ffffea00075ec720 ffffea000720e660 ffff8801d5add900 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8801d2c59480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801d2c59500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8801d2c59580: fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc ^ ffff8801d2c59600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801d2c59680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================